Stupid Question - Someone Explain Networking Notation/Terminology to Me

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svet-am

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When I see a subnet written as:

10.0.0.0/8 or 192.168.0.0/16

What does the notation with the slash mean? I have pieced together that it has something to do with the subnet but I have not found a place that explains this at length.

I *never* used this terminology when I was going through school in my networking classes and I'm not an IT geek (I am a IC silicon engineer) so I'm not sure how it all goes together. I've always historically specified it as two components: the base IP address and then a subnet but the notation above appears to communicate both in a single line.
 
It's dotted decimal notation followed by a slash which is the CIDR notation for the subnet mask. The number after the slash represents the number of bits in the subnet mask. So a /29 would be a 255.255.255.248 mask. Make sense?
 
Ah,yes. That makes perfect sense. I had never heard of CIDR notation before.
 
Yeah, it's just another way of representing the subnet mask. It equals the number of ones in the mask when converted to binary.

So, for example, a /24 = 255.255.255.0 = 1111111 1111111 11111111 00000000
A /29 = 255.255.255.248 = 11111111 11111111 11111111 11111000

The Wiki for CIDR does a decent job of elaborating on how the mask relates to actually defining subnets and the addresses they contain.
 
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